Conducting polymers have been used to modify the electrode surface and to immobilize the enzymes to construct biosensors for the detection of biomedically important species such as glucose, nitric oxide, histamine, etc. We will continue to use this approach to develop bioelectrodes which can catalytically reduce biomedically relevant species, and eventually develop a sensitive transducer for the detection of those species. For the detection of NO we will construct microsensors using both conducting polymers, and hemoprotein enzymes. Hemoproteins including hemoglobin (Hb), myoglobin (Mb), and cytochrome c peroxidase as well as the mutants of these proteins will be used to modify the surface of microelectrodes for an effective catalytic reduction of NO at less negative potentials that should minimize the effects of such interferents as nitrite, nitrite, and ascorbic acid. Since this type of electrodes use reductive potentials, the effects of catecholamines on the detect of NO can be eliminated. Conducting polymers using both polyhemin and polyhematin will be electrochemically coated on carbon fiber electrodes for the preparation of microsensors of the determination of NO. The utility of these electrodes will be tested in cell cultures. Spectroscopic methods including laser-Raman, FT-IR, and UV-visible absorption will be used to study the conformation of protein films on the electrode and also to elucidate the structural changes occurring under the different conditions including applied potential, pH, and in the presence of such species as NO and O2. We also plan to construct electrochemical amine sensors which are based on tryptophan tryptophylquinone (TTQ)- containing quinoproteins such as methylamine dehydrogenase (MADH) and aromatic amine dehydrogenase (AADH). Conducting polymers such as polypyrrole (PPy) will be used as a matrix to immobilize these enzymes on gold electrodes. These sensors will be characterized for the detection of dopamine, histamine, and other primary aliphatic and aromatic amines.